Effect of ERCC1 polymorphisms on the response to platinum-based chemotherapy: A systematic review and meta-analysis based on Asian population

Background Platinum-based chemotherapy is one of the most common treatments for many cancers; however, the effect of chemotherapy varies from individual to individual. Excision repair cross complementation group 1 (ERCC1) is widely recognized as a key gene regulating nucleotide excision repair (NER) and is closely associated with platinum response. Many studies have yielded conflicting results regarding whether ERCC1 polymorphisms can affect the response to platinum and overall survival (OS). Therefore, it is necessary to perform a meta-analysis of patients with specific races and cancer types. Methods Eight databases (EMBASE, PubMed, Cochrane Library, Chinese National Knowledge Infrastructure, Scopus, VIP, China Biology Medicine disc and Wanfang databases) were searched. Results were expressed in terms of odds ratios (ORs), hazard ratios (HRs) and 95% CIs. Results In this study, rs11615, rs2298881 and rs3212986 SNPs were studied. In the comparison between CT and TT on the response to platinum, esophageal cancer [I2 = 0%, OR = 6.18, 95% CI(1.89,20.23), P = 0.003] and ovarian cancer [I2 = 0%, OR = 4.94, 95% CI(2.21,11.04), P<0.001] showed that the rs11615 CT genotype predicted a better response. In the comparison between CC and TT, ovarian cancer [I2 = 48.0%, OR = 6.15, 95% CI (2.56,14.29), P<0.001] indicated that the CC genotype predicted a better response. In the meta-analysis of OS, the CC genotype was related to longer OS than TT in ovarian cancer [TT vs CC: I2 = 57.7%, HR = 1.71, 95% CI (1.18, 2.49), P<0.001]. Conclusion The ERCC1 rs11615 polymorphism was related to the response to platinum and OS, but the correlation is based on specific cancer types in the Asian population.


Introduction
Platinum-based chemotherapy is the standard treatment for many cancers, such as ovarian cancer, gastric cancer, esophageal cancer, osteosarcoma, etc. Despite the clear clinical benefit of platinum, some patients still exhibit drug resistance and these patients are increasing with increasing treatment lines. Some studies have shown this phenomenon can be explained by the nucleotide excision repair (NER). DNA damage by platinum is the main anti-cancer mechanism of platinum [1,2], and the damage can be repaired by the NER pathway [3]. Therefore, individual differences in NER capacity will lead to individual differences in response to platinum and thus to different prognoses. It would certainly benefit patients and clinicians if we could predict the response of patients to platinum before they receive platinum-based chemotherapy. Platinum-sensitive patients receive platinum-containing chemotherapy, while platinum-insensitive patients receive nonplatinum chemotherapy or other treatments. It can not only help clinicians to make decisions, but also reduce the pain caused by treatment. Excision repair cross complementation group 1 (ERCC1) component is a mammalian endonuclease that cleaves damaged DNA strands during the repair process of NER and interchain crosslinking. Detection of ERCC1 polymorphisms is expected to predict the efficacy of platinum-based chemotherapy. Two sub-pathways of NER, called global genome repair (GGR) and transcription-coupled repair (TCR), can be mentioned. DNA adducts including those induced by cisplatin are repaired by the nucleotide excision repair (NER) pathway [4]. ERCC1 is a subunit of the damaged 5 0 -side DNA endonuclease [5]. Following ERCC1-XPF nuclease mediated 5 0 incision, the damaged oligonucleotide is excised and appears to bind to one or more components of the repair complex.
Many studies have found conflicting effects of ERCC1 polymorphisms on the platinum response. Gradually, it became clear that the cause of this conflict was ethnic differences. In studies examining the relationship between ERCC1 polymorphisms and the responsiveness of patients with non-small cell lung cancer treated with cisplatin, the results showed that ERCC1 polymorphisms were not associated with platinum responsiveness and there was no evidence of a potential prognostic role in a Caucasian population [6,7]. While in Asian population, the T allele is a biomarker of low objective response, short progression free survival and overall survival (OS) in patients with gastric, osteosarcoma, ovarian and colorectal cancer [8][9][10][11]. So it is necessary to conduct a separate study on the impact of ERCC1 polymorphisms on platinum response and prognosis in Asian populations.
Currently, the most studied SNPs are rs11615, rs2298881 and rs3212986. Because the current study showed that the results of ERCC1 SNPs as a predictor of platinum treatment response and prognosis were contradictory, we performed a systemic review and meta-analysis to assess the evidence of effects of ERCC1 rs11615 C>T, rs2298881C>A and rs3212986 C>A SNPs on the efficacy of platinum-based chemotherapy and overall survival.

Literature search
The systematic review was performed according to the Meta-Analysis of Observational Studies in Epidemiology (i.e., MOOSE), Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement and protocol. The systematic review protocol was registered with the international prospective register of systematic reviews (PROSPERO): CRD42022339301.
Two reviewers (CH J and ZL Z) independently searched databases including EMBASE, PubMed, Cochrane Library, Chinese National Knowledge Infrastructure (CNKI), Scopus, VIP, China Biology Medicine disc (CBM) and Wanfang from inception to June 2022. The search strategy is displayed in the S1 Table. The search time was from the establishment of the database to June 10, 2022. Two reviewers (CH J and DN Z) independently screened the titles and abstracts of all retrieved records to exclude irrelevant studies. The remaining studies were assessed by reading the full text. Any disagreement was resolved by consensus or by involving an arbiter (XQ W).

Study selection
Inclusion criteria: (1) Population: Asian patients who were included in detection (primary detection) or being followed for recurrent disease and had cancer recurrence detected in histopathology. Patients who were receiving chemotherapy including cisplatin, carboplatin, oxaliplatin or nedaplatin. (2) Intervention: ERCC1 polymorphisms, including rs11615 (CT vs CC vs TT), rs3212986 (AA vs CA vs CC) and rs2298881 (AA vs CA vs CC). (3) Control: each phenotypic data was served as a comparator with the other two (rs11615: CT vs CC vs TT; rs3212986: AA vs CA vs CC and rs2298881: AA vs CA vs CC). (4) Outcome: Primary outcome is served as the response to platinum-based chemotherapy in each SNP. After receiving platinum containing chemotherapy, patients with CR or PR were defined as having good response, while those with SD or PD were defined as having poor response. The secondary outcome was defined as OS for each SNP. OS was defined as the time from the observation point to death from any cause. (5) Study design: cohort and case control studies.
Exclusion criteria: All studies with mutated bases in gene fragments that did not meet the requirements listed in the inclusion criteria were excluded. We also excluded studies reporting data on laboratory developments tests as well as reviews, letters to editors, editorials, study protocols, case reports, brief correspondence, and articles published in languages other than English or Chinese. The references of all papers included were scanned for additional studies of interest.

Data extraction
Three investigators independently extracted the following information from the included articles: author name, publication year, country, chemotherapy regimen, number of patients, cancer species, number of good responses (CR+PR) and poor response (SD+PD), hazard ratio and 95% confidence interval between different genotypes and overall survival. The Newcastle-Ottawa Quality Assessment Scale was used to assess the quality of each of the included studies. Any discrepancy was resolved by discussion or by involving an arbiter (XQ W).

Trial sequential analysis (TSA)
We assessed the risk of false positives or false negatives by TSA in a meta-analysis. Sequential monitoring boundaries were established to limit Type I error to 5% and Type II error to 20% to detect responsiveness to platinum and OS of patients under various models. When cumulative Z curves crossed conventional boundaries and trial sequential monitoring boundaries and the sample size reached the accrued information size (AIS), the expected intervention effect may reach a sufficient level of evidence. TSA was completed using the Stata, version 13.0, R package "foreign" and "ldBounds".

Statistical analysis
The effect estimates of interest were the OR (95%CI) in the meta-analysis of response to platinum and HR (95%CI) in the meta-analysis of overall survival. Studies exploring the response to platinum and overall survival of cancers were analyzed separately, and subgroup analyses were performed according to different cancer species. Assessment of heterogeneity was performed using Higgins I 2 ; I 2 greater than 50% and a P value less than 0.10 suggested significant heterogeneity, and a random effect model was applied; I 2 less than 50% and a P value more than 0.10 suggested tolerable heterogeneity, and a fixed effect model was applied. Sensitivity analysis was performed by sequentially omitting each study to examine the robustness of the results. Potential publication bias was evaluated using a funnel plot (number of studies � 10) and Begg's and Egger's tests. If significant publication bias existed, the trim and fill method was performed to validate the robustness of the meta-analysis results. Sensitivity analysis adopts the row-by-row division method. All statistical analyses were calculated via Stata, version 13.0 (StataCorp, College Station, TX). P values < 0.05 and Bonferroni-corrected p < 0.017 in studies with the response to platinum as the outcome (Results 2) and p values <0.05 and Bonferroni-corrected p < 0.025 in studies with OS as the outcome (Results 3), were defined as statistically significant, except those for heterogeneity.

Literature research
We identified 42 studies in CBM, 228 studies in Embase, 274 studies in the PubMed database, 32 studies in the Cochrane Library, 218 studies in the CNKI database, 86 studies in the VIP database, 20 studies in Scopus, and 306 studies in the Wanfang database. The flowchart of study selection is shown in Fig 1, and 27 studies were included in our meta-analysis. Among these studies, 26 studies reported the relationship between the ERCC1 rs11615 (C>T) polymorphism and platinum reactivity, 8 of which reported the effect of the rs11615 (C>T) polymorphism on OS. Six studies reported the relationship between the rs229981 (C>A) polymorphism and the response to platinum, 3 of which focused on the influence of the rs229981 (C>A) polymorphism on OS. Ten studies observed an association between the rs3212986 (C>A) polymorphism and the response to platinum, 6 of which also reported the rs3212986 (C>A) polymorphism and OS. The characteristics of these studies are summarized in Table 1. Newcastle-Ottawa Scale (NOS) assessments are shown in Table 2.
It should be noted that there was only one study in the colon, nasopharyngeal and cervical cancer groups.
The funnel plot was basically symmetrical (Fig 2(D)), and Begg's test and Egger's test showed P = 0.243 and 0.251, respectively, indicating no publication bias. The TSA results showed that the enrolled studies were adequate (Fig 2(E) Fig 3(B). It should be noted that there was only one study in the colon, nasopharyngeal and cervical cancer groups.
The funnel plot was basically symmetrical (Fig 3(C)). Begg's test and Egger's test showed that P = 0.675 and 0.110, respectively, indicating that there was no publication bias. The  sensitivity analysis showed that the result was reliable (Fig 3(D)). The TSA results showed that the enrolled studies were adequate (Fig 3(E)).

Homozygous model (CC vs TT).
Number of studies and people involved in the study as described in 2.1.1. ERCC1 rs11615 CC genotype was related to a good response to platinumbased chemotherapy. Homozygous model (CC vs TT): I 2 = 53.6%, random effect model was   Fig 4(B). It should be noted that there was only one study in the colon, nasopharyngeal and cervical cancer groups. The funnel plot was basically symmetrical (Fig 4(C)). Begg's test and Egger's test showed that P = 0.675 and 0.175, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was reliable (Fig 4(D)). The TSA results showed that the enrolled studies were adequate (Fig 4(E)).  [16,17,19,20,37,38], involving 1678 patients were included. There were 3 studies on gastric cancer, 2 on osteosarcoma and 1 on ovarian cancer. The CA+AA and CC genotypes showed no difference in platinum sensitivity.

PLOS ONE
The funnel plot was basically symmetrical (Fig 5(C)). Begg's test and Egger's test showed that P = 0.452 and 0.829, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was robust (Fig 5(D)). The TSA results showed that the enrolled studies were not adequate and need to be verified by more relevant studies (Fig 5(E)).

Heterozygous model (CA vs CC).
Number of studies and patients involved in the study as described in 2.

PLOS ONE
The funnel plot was basically symmetrical (Fig 6(C)). Begg's test and Egger's test showed that P = 0.462 and 0.860, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was robust (Fig 6(D)). The TSA results showed that the enrolled studies were adequate (Fig 6(E)).  Fig 7(B).

Homozygous model (AA vs CC). Number of studies and patients involved in the study
The funnel plot was basically symmetrical (Fig 7(C)). Begg's test and Egger's test showed that P = 1.000 and 0.969, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was robust (Fig 7(D)). The TSA results showed that the enrolled studies were adequate (Fig 7(E)).

The rs3212986 A/C polymorphisms in ERCC1. 2.3.1 Dominant model (CA+AA vs. CC).
The rs3212986 polymorphism has a wild-type C allele and variant A allele. A total of 9
The funnel plot was basically symmetrical (Fig 8(C)). Begg's test and Egger's test showed that P = 0.592 and 0.993, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the results were robust (Fig 8(D)). The TSA results showed that the enrolled studies were adequate (Fig 8(E)).

Heterozygous model (CA vs CC).
Number of studies and patients involved in the study as described in 2.3.1. The CA and CC genotypes showed no difference in response to platinum.  Fig 9(B).
The funnel plot was basically symmetrical (Fig 9(C)). Begg's test and Egger's test showed that P = 0.251 and 0.391, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was robust (Fig 9(D)). The TSA results showed that the enrolled studies were adequate (Fig 9(E)).  Fig 10(B).

Homozygous model (AA vs CC). Number of studies and number of patients involved
The funnel plot was basically symmetrical (Fig 10(C)). Begg's test and Egger's test showed that P = 0.466 and 0.336, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was robust (Fig 10(D)). The TSA results showed that the enrolled studies were adequate (Fig 10(E)).  Fig 11(B). There was only one study in the esophagus.
Begg's test and Egger's test showed that P = 0.902 and 0.530, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was reliable (Fig  11(C)). TSA showed that the AIS was 1569, and the sample size met the requirement (Fig 11  (D)).
Begg's test and Egger's test showed that P = 0.548 and 0.398, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the results were not robust (Fig 11(G)). TSA showed that the AIS was 1360, and the sample size met the requirement (Fig 11(H).

The rs2298881 A/C polymorphisms. 3.2.1 Homozygous model (AA vs CC).
A total of 3 studies [19,20,38] were included in the homozygous model, involving 663 patients. There were 3 studies on gastric cancer, 2 on osteosarcoma and 1 on ovarian cancer. Homozygous  Fig 12(A). Because there were too few studies included, the meta-analysis was conducted again after the study was trimmed and completed to verify the sensitivity. HR = 1.06, 95% CI (0.68,1.67), P = 0.800, as shown in Fig 12(B). AA vs CC was not related to overall survival. TSA showed that the AIS was 663, and the sample size met the requirement (Fig 12(C).

Heterozygous model (AC vs CC).
Number of studies and number of patients involved in the study as described in 3.2.1. AC vs CC was not related to overall survival. Heterozygous model (AC vs CC): I 2 = 0%, fixed effect model was used, HR = 1.17, 95% CI (0.80,1.73), P = 0.416, as shown in Fig 12(D). The result of the meta-analysis after trim and fill showed that HR = 1.10, 95% CI (0.77,1.56), P = 0.616 (Fig 12(E)). TSA showed that the AIS was 663, and the sample size met the requirement (Fig 12(F).

PLOS ONE
Begg's test and Egger's test showed P = 1.000 and 0.580, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was reliable (Fig 13(B)). TSA showed that the AIS was 1159, and the sample size met the requirement (Fig 13(C)).

Homozygous model (AA vs CC).
Number of studies and number of patients involved in the study as described in 3.3.1. Homozygous model (AA vs CC): I 2 = 59.4%, random effect model was used, HR = 1.82, 95% CI(0.87,3.80), P = 0.109, as shown in Fig 13(D).
Begg's test and Egger's test showed that P = 0.806 and 0.422, respectively, indicating that there was no publication bias. The sensitivity analysis showed that the result was reliable (Fig 13(E)). TSA showed that the AIS was 1159, and the sample size met the requirement (Fig 13(F)).

Discussion
The study explored the effects of ERCC1 rs11615, rs2298881 and rs3212986 polymorphisms on platinum responsiveness and OS. Platinum responsiveness may reflect short-term effects, whereas the OS reaction can reflect long-term effects. These two results are correlated, but not necessarily consistent, and therefore both need to be evaluated. In ERCC1 rs11615, the CT and

PLOS ONE
CC genotypes predicted a better response to platinum in ovarian cancers than the TT genotypes. Polymorphisms were also associated with OS. The CC genotype was associated with longer overall survival in ovarian cancer patients than in TT patients. In ERCC1 rs2298881 and rs3212986, the A/C polymorphism was not related to the response to platinum and OS.

PLOS ONE
The ERCC1 protein is an excision nuclease that acts within the NER pathway and is involved in platinum metabolism. There are many mechanisms of platinum resistance, and NER is the main mechanism leading to moderate resistance [39]. From the above results, it is easy to see that the effect of ERCC1 polymorphism on platinum responsiveness is related to cancer type. This may be related to the influence of the NER pathway on the occurrence and development of different cancers. NER is a key pathway for dysregulated DNA repair in esophageal adenocarcinoma [40], ovarian cancer [41] and gastric cancer [8]. ERCC1 rs11615, rs229881 and rs3212986 are the most intensively studied SNPs. ERCC1 is a key rate-limiting enzyme in the multistep NER process. ERCC1, in collaboration with the XPF protein, is involved in DNA lesion recognition. Therefore, functional ERCC1 SNPs may contribute directly to phenotypes of drug sensitivity by modifying the function of related genes and reflecting platinum sensitivity as an innate trait [8].
The TT subtype of rs11615 was associated with platinum resistance, whereas CT and TT containing the T allele were associated with shorter OS. This result can be explained by PLOS ONE biological significance. The rs11615 T allele of the ERCC1 polymorphism was found to be associated with high mRNA expression of the corresponding gene [42]. Functional studies confirmed the substantial effect of the ERCC1 rs11615C>T SNPs on the phenotype of NER capacity [42][43][44], which leads to enhanced DNA repair capacity and even to the development of platinum resistance.
The reasons for this significant ethnic difference are unclear which may be due to significant race-specific differences in linkage disequilibrium (LD) between rs11615 SNP and other nearby alleles that may cause platinum resistance [45]. The difference results in a possible lower prognostic and predictive value of the rs11615 SNP in African Americans and Africans than in Caucasians and Asians. In the Asian (CHB+JPT) population, at least five upstream polymorphisms within or directly adjacent to the ERCC1 gene were associated with rs11615. In addition to altering ERCC1 expression, phenotypic alterations in rs11615 may also lead to alterations in adjacent genes [46].

PLOS ONE
Our study not only analyzed the platinum sensitivity and prognosis of different SNPs but also compared different cancers horizontally. It can be seen that different cancers and different SNPs have varying effects on platinum sensitivity and prognosis. Ovarian cancer identified in this study was closely related to ERCC1 gene polymorphisms. Ovarian cancer patients do benefit from DNA damage repair pathway inhibitors, such as Rucaparib [47][48][49], Olaparib [50][51][52] and Niraparib [53][54][55][56]. These drugs target DNA damage repair (DDR) pathways, such as BRCA1/2 mutation and homologous recombination deficiency. In addition, HRR deficiency can also cause hereditary ovarian cancer [57]. All the above evidence suggests that ovarian cancer is a genomically unstable tumor, which may be the reason why the NER pathway represented by ERCC1 affects it more significantly. The lack of a specific DDR pathway may lead to mutation or chromosomal rearrangement and other consequences, promoting genomic instability and tumorigenesis [58]. Other similar studies have examined the relationship between only one SNP and one type of cancer. Our study focused on different cancer types and races. The limitation of this study is that some results may have boundary effects. But all of the results are reliable through sensitivity analysis. We did not search for documents published in other languages except English and Chinese, which may lead to bias due to language restrictions. In clinical practice, clinicians may prefer to select chemotherapy schemes other than platinum containing chemotherapy for patients with ERCC1 polymorphism rs11615 TT genotype, such as early use of PARP inhibitors and anti-angiogenesis, especially in ovarian cancer.

Conclusion
The ERCC1 rs11615 CT and CC genotypes predicted a better response to platinum than the TT genotype in esophageal and ovarian. The CC genotype was related to longer overall survival than TT in ovarian cancer. The ERCC1 rs2298881 and rs3212986 A/C polymorphisms were not related to the response to platinum and OS.